000
AXPZ20 KNHC 281604
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU JUL 28 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS WESTWARD FROM PANAMA AT 09N79W TO 
DEVELOPING LOW PRES OF 1009 MB AT 09N90W...WITH THE TROUGH AXIS 
TURNING SLIGHTLY NW TO 11N105W THEN ABRUPTLY SW TO 8N122W WHERE 
LOW LEVEL WINDS INDICATE THAT THE ITCZ AXIS BEGINS AND CONTINUES 
W TO 8N131W AND TO BEYOND 7N140W. OVERCAST MULTILAYERED CLOUDS 
ARE OBSERVED OVER THE ENTIRE AREA E OF 95W. SCATTERED STRONG 
CONVECTION IS LOCATED FROM 4N-7N E OF 84W...AND WITHIN 60 NM 
OF THE MONSOON TROUGH BETWEEN 90W-93W. 

SCATTERED MODERATE ISOLATED/STRONG CONVECTION IS N OF THE ITCZ
AXIS WITHIN 30 NM OF A LINE FROM FROM 12N134W TO 11N140W...AND
ALSO WITHIN 60 NM OF THE MONSOON TROUGH BETWEEN 90W-93W.

SCATTERED MODERATE CONVECTION IS N OF THE ITCZ WITHIN 30 NM OF
13N128W...AND N OF THE MONSOON TROUGH WITHIN 30 NM 13N112W.

...DISCUSSION...

AN UPPER RIDGE EXTENDS SW AND W FROM THE TEXAS PANHANDLE TO A 
CREST AT 32N124W AND HAS HALTED THE EASTWARD ADVANCE OF A DEEP 
LAYERED TROUGH EXTENDING FROM CENTRAL CALIFORNIA SW TO A SMALL 
CYCLONIC CIRCULATION NEAR 31N124W AND SW TO A BASE AT 
17N134W...WITH INDICATION OF AN UPPER CYCLONE DEVELOPING AT 
27N131W. NORTHERLY SURFACE WINDS ARE EXPECTED TO INCREASE 
OVERNIGHT AND INTO FRI MORNING WITH SEAS BUILDING TO 9 FT W OF 
THE TROUGH AS THE LEADING EDGE OF A LARGE NLY SWELL TRAIN N OF 
THE AREA BEGINS TO SURGE SWD INTO THAT PORTION OF THE 
DISCUSSION AREA. A RATHER ELONGATED N TO S UPPER LEVEL 
ANTICYCLONE IS JUST W OF THE DEEP LAYERED TROUGH AND W OF THE 
AREA AT 25N142W...WHILE AN UPPER ANTICYCLONE IS TO THE SE OF THE 
DEEP LAYERED TROUGH AT 18N118W...WITH A RIDGE EXTENDING SW TO 
14N131W  A CREST AT 12N141W...AND ANOTHER RIDGE SE TO 16N108W.
A SMALL UPPER CYCLONE IS DEVELOPING JUST NE OF THE RIDGE AT 
21N113W.

UPPER LEVEL DIFFLUENCE ON THE SW PERIPHERY OF A N TO S RIDGE
ACROSS THE YUCATAN PENINSULA AND GUATEMALA IS HELPING TO MAINTAIN
AN AREA OF WIDESPREAD SCATTERED STRONG CONVECTION OVER THE FAR 
EASTERN PORTION OF THE AREA S OF THE MONSOON TROUGH AS DESCRIBED
ABOVE. THE RESULTANT DEBRIS MOISTURE IS OBSERVED TO THE S AND SW 
OF MEXICO AND CENTRAL AMERICA AS IT IS BEING ADVECTED WESTWARD 
BY MODERATE UPPER LEVEL EASTERLY WINDS. AS IT APPROACHES 117W IT 
ERODES IN A DRIER AND STABLE AIR MASS. THIS DRY AIR IS 
ASSOCIATED WITH AN EXPANSIVE AREA OF MODERATE TO STRONG 
SUBSIDENCE NOTED ON SATELLITE WATER VAPOR TO COVER THE AREA N OF 
19N W OF 119W...AND S OF 9N W OF 117W. ANOTHER BATCH OF DRY 
STABLE AIR IS NOTED TO THE N OF 15N AND E OF 119W.

THE SW CONUS RIDGE WILL BUILD A LITTLE FURTHER W AND PUSH THE 
UPPER CYCLONE NEAR 27N130W A LITTLE FURTHER W OVER THE NEXT DAY 
OR SO.
 
SOUTHWESTERLY MONSOONAL FLOW HAS INCREASED TO 15-20 KT ACROSS 
THE WATERS TO THE S OF 7N AND E OF 89W WITH COMBINED SEAS OF 
8-10 FT IN A SW SWELL. CROSS EQUATORIAL SW SWELL...SEAS TO 9 
FT...SURROUNDS THIS AREA OF ENHANCED MONSOON FLOW...GENERALLY TO 
THE S OF 15N E OF 109W. STATIONARY LOW PRESSURE IS FORMING ALONG 
THE MONSOON TROUGH NEAR 9N91W AND IS EXPECTED TO SLOWLY MOVE
WESTWARD THROUGH SAT AND POSSIBLY BECOME MORE CONSOLIDATED DUE
TO THE COMBINATION OF THE LARGE MONSOON GYRE THERE ACQUIRING
IMPETUS FROM A TROPICAL WAVE THAT MOVES OFF SE MEXICO AND INTO 
THE FAR EASTERN PACIFIC WATERS.

CROSS EQUATORIAL SW SWELLS ARE FORECAST TO CONTINUE OVER THE 
WATERS S OF 10N MAINLY BETWEEN 82W AND 115W OVER THE NEXT 48 
HOURS.
   
$$
AGUIRRE